30-seconds-of-code: I think it will change the allEqual definition in docs

[OhIAmFine]

As I can see in the README, the allEqual definition is like that:

  const allEqual = arr => arr.every(val => val === arr[0]);

But when I test allEqual([NaN, NaN]), it will return false,

I think it need change the definition like that:

 const allEqual = arr => arr.every(val => Object.is(val, arr[0]));

when I test allEqual([NaN, NaN]), it will return true as I expect.

I just a poor learner at js, so please point out my mistake if I was wrong.

[Chalarangelo]

That's quite an interesting edge-case, actually, due to the fact that NaN is not equal to itself. Object.is() seems like a solution, but we should check if it has any other side-effects before changing the allEqual method.

In any case, this is a very interesting observation and we should do something about it - either update the code or add a comment about the edge-case.

[OhIAmFine]

Ok, that's your attention

[skatcat31]

If we do update the code it would be considered a breaking change because NaN is meant to be not equal to itself. So if we do go to the more "stable" Object.is() then we will need to note it

[Chalarangelo]

@skatcat31 We should add a comment either way. I do agree that NaN's behavior is essentially by-design in this snippet. Maybe we just add a note about it and go our merry way?

[skatcat31]

Adding a comment either way is a good step, and I think keeping it the way it is now and noting it would be better.

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